This study proposes a quantitative assessment method to ascertain urban square potential at 12 gates of the historic city wall where different typologies, characteristics and periodic features are observed in Fatih district of Istanbul. The quantitative assessment method is based upon a series of indexes including 7 factors in total consisting of 35 indicators. The proposed method developed an “urban square potential index”, making use of “transport and accessibility”, “convex size”, “built-up environment”, “purpose of use and density”, “morphology”, “landscaping character” and “identity” factors. This index enables assessment of a square according to a) historical-cultural heritage richness and identity, b) functional diversity, c) accessibility, and d) vitality and spatial quality. This paper presents a base for “decision-support system” for decision-makers in determination of the most suitable square with a limited budget, time, labor and equipment during urban square development, design and improvement activities. Furthermore, it allows determination and implementation of the necessary interventions/improvements in order for the available undefined urban spaces to gain urban square functions.